Gun perforator for well casing



Patented Sept. 3, 1946 UNITED STATES PATENT OFFICE GUN PERFORATOR FOR WELL CASING Mordica 0. Johnston, Glendale, Calif.

Application November 27, 1944, Serial No. 565,261

4 Claims.

This invention relates to oil well tools, and particularly pertains to a gun perforator for well casing.

In gun type perforators for well casing, as shown in my Patent No. 2,048,451, issued July 21, 1936, and entitled Casing perforating gun, a substantially cylindrical body member was provided which was lowered into a well casing on a string of pipe, the body member being formed with a plurality of firing chambers sealed at their outer ends by a projectile and a barrel and within which an explosive charge was ignited by electrically controlled firing mechanism. In other types of perforating guns the barrel has been made with interconnecting firing chambers within which the explosive charges contained in the several chambers are successively ignited as fire passes through a duct from one chamber to the other. In all of these types of gun perforators heretofore mentioned the construction of the firing chambers and the projectiles therefor have been disposed at successive spaced intervals along the body member of the gun and with the axes of the barrels of contiguous firing units disposed at wide angles to each other so that the firing chambers could be properly sealed against the hydrostatic head of liquid present in the well bore. This arrangement is not altogether practical since the perforations formed in the well casing cannot be closely spaced. It is desirable,

therefore, to design a gun perforator body carrying firing chambers which may be spaced closely to each other and disposed in any desired angular arrangement radially of the perforator body, whereby a suitable pattern of perforations may be formed at each firing period of the gun. It is the principal object of the present invention, therefore, to provide a gun perforator body having individual firing chambers and barrels so constructed as to receive a novel projectile adapted to seal the firing chamber and to insure suitable firing power while the radial angular positions of the barrels are disposed close together and need not be at wide angle to each other as is now usually the case.

The present invention contemplates the provision of a gun perforator body substantially cylindrical in shape and of a diameter to be lowered conveniently through a well casing to a point of operation, said body being formed with a plural ity of explosive chambers at desired spaced levels throughout the length of the gun body and being disposed at any desired degree of axial spacing with relation to each other, the firing chamber being equipped with a removable barrel cooperating with a special projectile acting to seal the firing chamber and to retard movement of the projectile until a desired firing power has been developed within the confined firin chamber.

The invention is illustrated by way of example in the accompanying drawing in which:

Figure 1 is a view in section and elevation generally indicating the application of the gun perforator to a well bore and its casing.

Fig. 2 is an enlarged view in central vertical section showing the construction and arrangement of the firing chambers and barrels incorporated within the perforator body.

Fig. 3 is an enlarged view in elevation with parts broken away showing the projectile and its sealing means.

Referring more particularly to the drawing, l0 indicates a string of pipe fitted with a pin II at its lower end to receive a box section l2. Fastened into the lower end of the box section is a cylindrical firing rod l3 carrying a firing unit I4. This unit is here shown as fitted with yieldable shoes l5 by which it is centered in a well casing IS. The unit may be of any desired construction to ignite a firing charge within a breech section 11. The breech section is formed with a lower threaded pin portion I8 which engages a threaded counterbore 19 within the gun perforator body generally indicated at 20. This body may comprise any desired number of perforating units 2| which are threaded to each other at contiguous ends and are longitudinally aligned. The lowermost one of these units is fitted with a cap 22. This cap forms a protecting end for the unit and also seals the lower end of a firing duct 23. The firing duct extends longitudinally and centrally through each of the perforating units 2|, and since the units 2| are fastened end to end the firing duct 23 will extend entirely from the breech section I! to the lowermost end of a duct 23 which is covered by the cap 22. Disposed along the length of each of the body members 2| is a series of firing chambers 24. These chambers extend transversely within a body member 2| and are disposed radially with relation to the longitudinal axis of the body member and the firing duct 23. The firing chambers 24, as shown in Fig. 2 of the drawing, are cylindrical in cross-section and are of a length to intersect the longitudinal axis of the body member 2| and the duct 23 so that sections of the duct 23 will establish communication between successive firing chambers. The longitudinal axis of the firing chambers 24 may be arranged at any selected degree so that any desired firing pattern may be produced.

Each of the firing chambers 24 has a cylindrical side wall 25 which terminates in a dead end wall 26 at one end. At the opposite end of the firing chamber a reduced outlet bore 2'! is formed which is of circular section. The outer end of this bore terminates in a sealing seat 28 which is at the bottom of an enlarged threaded bore 29 designed to receive a removable barrel 30. This barrel is formed with a muzzle bore 3| through which a projectile passes and by which the projectile is directed to impinge against the face of the well casing. The outer end of the threaded bore 29 is finished by a counterbore 32 which is of a depth sufiicient to shield the convexed end 33 of the barrel 30. The opposite end of the barrel 30 is formed with a cylindrical counterbore 34 which agrees in diameter with the bore 28 formed in the perforator gun body 2!,

said bores being concentric with the longitudinal axis of the firing chamber 24 and the barrel 3B.

The firing chamber and barrel construction, as previously described, are designed to accommodate a projectile 35, a sealing and shear ring 36, and an explosive charge 31'. The projectile is formed with a main cylindrical portion 38 which agrees substantially in diameter with the muzzle bore 3|. One end of the portion 38 is formed with a nose 39 which may be of any desired shape, depending upon the perforating Work to be done. The opposite end of the projectile is formed with an annular groove 43 which occurs a desired distance from the exact end of the projectile and is formed in the cylindrical face of the portion 38. This groove has opposite'square shoulders ll and 42 and an intermediate cylindrical face. The depth of the groove is determined, for a purpose to be hereinafter described, and is represented by a critical dimension. At the exact end of the portion 38 of the projectile 35 a short cylindrical portion 38 occurs. This is of the same diameter as the main portion 38 and provides an end face 43 against which the explosive force of the explosive charge 3! is directed.

Made separately and subsequently mounted upon the projectile 35 is the sealing ring 36. This ring is cup-shaped and is formed with an outer cylindrical face 44 which agrees substantially with the diameter of the bore 28 in the perforator body 2! and also agrees in diameter with the counterbore 34 formed in the barrel 30. The length of the sealing ring 36 is slightly greater than the combined lengths of the bore 28 in the gun perforator body 2| and the counterbore 34 in the barrel 30. The ring 36 is formed at one end with a cylindrical bore 45 which agrees in diameter with the diameter of the cylindrical portion of the recess ll) which is formed on the body portion 38 of the projectile 35-. The length of the cylindrical bore 45 agrees in dimension with the distance between the shoulders 4i and 42 of the recess 40 on the projectile 35 and is defined by the end face d6 of the ring and a shoulder 41 within the ring. Th shoulder '41 has a diameter agreeing with the diameter of the portion 38 of the projectile 35. A tapered counterbore 48 is formed within the ring 36 and extends from the shoulder 41 to the end face M) of the ring, which face is parallel to the opposite end face 46. The taper of the side wall of the counterbore 48 is here indicated as being approximately nine degrees, for purposes to be hereinafter explained. It will of course be understood that this angle might be changed to create difierent conditions as desired. This forms an outwardly flaring 4 frusto-conical wall around and beyond the portion 38' of the projectile 35. V

In operation of the present invention the gun perforator is assembled as shown in Fig. 1 with a desired number of body sections 2| forming the gun perforator body 25. The gun is then loaded by introducing a charge of explosive 31' into each of the explosive chambers 24. This charge of explosive i here shown as being in the form of a cylindrical stick of explosive material having a diameter substantially agreeing with the diameter of the bore 21 leading from each of the explosive chambers 24. It will be recognized that the explosive elements 31 are of lesser diameter than the diameter of the explosive chambers 24, thus providing a combustion and expansion space 59 around the explosive charge 37 and within the chamber 24. The length of the stick of explosive 31 1s greater than the length of the explosive chamber 24, andin fact extends entirely through the bore 27 and rests against the end face 43 of theprojectile when the gun is loaded. Prior to loading the gun the projectiles 35 are assembled with the rings 36. The sealing and shear ring 35 is made of metal, and in View of the fact that its cylindrical bore 45 is less in diameter than the diameter of the cylindrical portion 38 of the projectile 35 it is necessary to force the projectile through the ring and to temporarily stretch the ring until the bore 45 registers with the recess 4d, at which time the reduced portion of the ring occurring between the faces 46 and 5! will snap into position between the shoulders M and 12 of the recess 40 and will form a tight seal therewith. The projectile and ring thus assembled, as shown in Fig. 3 of the drawing, is then positioned within the bore 28 of the body member 2| so that the end face 49 of the ring will rest against the bottom face of the bore 28. The barrel 3!) is then screwed in place with the body 38 of the projectile 35 extending outwardly within the muzzle bore 3!. As the barrel 3!) is screwed tightly into place within the threaded bore 29 the outermost portion of the ring 38 will register With the counterbore 34 in the end of the barrel and pressure will be exerted to form a tight seal between the barrel and the face 46 of the ring and a tight seal between the end of the bore 28 and the face 49 of the ring. At the same time the end face 42 of the projectile will be drawn against the end of the stick of explosive 37 so that the explosive will be held in place firmly. After the gun perforator has been completely loaded it may be lowered into the well to a desired level, after which the mechanism within the portion [4 is manipulated to produce initial ignition of explosive within the breech block ll. This explosive will then burn downwardly through the firing ducts 23 and successively although substantially simultaneously produce ignition of all of the explosive charges 31 in the various explosive chambers 24. When an explosive charge 31 is ignited it will begin to burn and create gaseous pressure within the chamber 24. The immediate movement of the projectile 35, however, will be restrained by the shear ring until sufficient firing power has been built up within the explosive chamber 24. This firing power is of course determined by the amount of explosive 31, the size of the explosive chamber 24, the thickness of the wall represented between the faces 46 and 41 of the sealing ring 35, and the character of the metal from which the ring is made. It is to be understood that while the sealing and shear ring 36 has been described as being separate from the projectile that in certain instances it might be found desirable to form it integral with the projectile. When the explosive force is sufficient to shear this wall thickness the projectile 35 will be released and will be forced outwardly through the muzzle bore 3i to strike the well casing or formation encountered in its path. Thus, the casing will be perforated, and if the firing power is great enough an opening will be made in the formation to facilitate in the flow of cognate fluid from the formation.

It will be understood that due to the fact that the firing duct 23 is disposed centrally of the body 2| it is possible to easily locate the firing chambers 24 and the barrels 39 in any desired angular radial relation to each other, since individual firing mechanism is not necessary and the explosive charges do not need to be wired individually. It will also be seen that due to the design of the sealing ring 39 and the parts between which it is gripped it is possible to seal the firing chamber against induction or eduction of fluids under pressure, Whether it be the gases developed within the firing chamber or the hydrostatic pressure of fluid within the well bore, and it is also to be pointed out that the design of the sealing ring 36 may be made to absolutely establish the magnitude of firing power developed within the explosive chamber 24 before the projectile is released and fired.

It will thus be seen that the gun perforator construction here disclosed makes it possible for projectiles of simple and cheap construction to be made and to be fired by an explosive which may be easily handled, and that furthermore the gun may be quickly and easily loaded and when fired will develop any desired firing power.

While I have shown the preferred form of my invention as now known to me, it will be understood that various changes may be made in combination, construction and arrangement of parts by those skilled in the art, without departing from the spirit of my invention as claimed.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a gun perforator, a body member having an explosive chamber therein to receive a charge of explosive, said chamber lying in a plane normal to the longitudinal axis of the body and intersecting said axis, the inner end of said chamber being closed and the outer end being formed with a restricted outlet opening, a seat formed around the outer end of the outlet opening to receive an annular flange portion of a projectile, a threaded bore extending outwardly beyond said seat, a threaded barrel having a central muzzle bore and adapted to be mounted within the threaded opening to receive the outer end of the projectile in the muzzle bore and to cooperate with the seat in the body member in engaging the flange of the projectile and thus holding the projectile until the firing power of the explosive shears said flange from the projectile.

2. In a gun perforator adapted to fire a projectile which is cylindrical in cross-section and which carries a sealing and shear ring adjacent the inner end thereof, a gun body adapted to be lowered into a well bore and having firing means associated therewith to be controlled from the ground surface of the well, an explosive chamber formed in the gun body, said chamber being of circular cross-section with its longitudinal axis disposed in a plane normal to the longitudinal axis of the body, one end of said chamber being closed and the opposite end being formed with a restricted outlet opening, a counterbore at the outer end of said outlet opening providing a sealing shoulder and against which shoulder the sealing and shear ring of the projectile rests, a threaded counterbore extending beyond the first named counterbore, and a threaded barrel adapted to be mounted within the threaded counterbore with its muzzle bore receiving the outwardly projecting portion of the projectile, the inner face of the barrel cooperating with the shoulder of the counterbore to grip the sealing ring.

3. In a gun perforator adapted to fire a projec tile which is cylindrical in cross-section and which carries a sealing and shear ring adjacent the inner end thereof, a gun body adapted to be lowered into a well bore and having firing means associated therewith to be controlled from the ground surface of the well, an explosive chamber formed in the gun body, said chamber being of circular cross-section with its longitudinal axis disposed in a plane normal to the longitudinal axis of the body, one end of said chamber being closed and the opposite end being formed with a restricted outlet opening, a counterbore at the outer end of said outlet opening providing a sealing shoulder and against which shoulder the sealing and shear ring of the projectile rests, a threaded counterbore extending beyond the first named counterbore, a threaded barrel adapted to be mounted within the threaded counterbore with its muzzle bore receiving the outwardly projecting portion of the projectile, and a counterbore in the inner face of the barrel to cooperate with the counterbore in the body to receive and grip the sealing and shear ring.

4. A gun perforator adapted to fire a cylindrical projectile having an enlarged annular cup-shaped ring on its trailing end, said gun including a firing unit, a cylindrical body member carried at the lower end thereof and being formed with a central firing duct communicating with the firing unit, a plurality of explosive chambers arranged at spaced intervals along the length of the body member and intersecting the firing duct whereby communication will be established between contiguous firing chambers, said firing chambers being circular in cross-section and having their inner ends closed, an opening at the opposite end of the firing chamber of reduced diameter, a counterbore at the outer end of said opening forming a fiat shoulder lying in a plane normal to the longitudinal axis of the chamber, an enlarged threaded opening extending outwardly and being disposed concentrically of the longitudinal axis of the firing chamber, a barrel formed with a central muzzle bore and threaded to be seated within said threaded bore, and a counterbore in the inner end of said barrel concentric with said muzzle bore and cooperating with the face of the counterbore within the body of the gun to grip the sealing and shear ring carried by the projectile and to thus seal the explosive chamber while restraining movement of the projectile until an explosive force has been created within the explosive chamber having sufiicient magnitude to shear the ring from the projectile.

MORDICA O. JOHNSTON. 

